Auto-focusing device with voice coil motor for position feedback and method for using same

Abstract

An auto-focusing device with voice coil motor for position feedback comprises a lens holder, a sensor holder, a permanent magnet set, a yoke and a base. The lens holder holds a lens barrel and is wound around with at least two coils wound in opposite directions. The sensor holder holds an image sensor. The permanent magnet set includes at least two permanent magnets stacked together with opposing poles to form a multi-pole permanent magnet set. The permanent magnet set is furnished on the periphery of lens holder and corresponds to the two coils on lens holder. The permanent magnet set is disposed on the yoke to form a close-loop magnetism so as to increase the density of magnetic lines and the efficiency of magnetic force, save power consumption, and extend the service life of device.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an auto-focusing device with voice coil motor for position feedback, more particularly an auto-focusing device having a voice coil motor on its auto-focus lens as power source and a magnetic sensor to detect the position of lens for position feedback during auto-focus of lens. [0003] 2. Description of the Prior Art [0004] As shown in FIG. 1, a standard camera 1 comprises a lens set 11, an optical sensor 12 and a focusing mechanism (not shown in the figure). The lens set 11 forms an image on optical sensor 12 by refracting the light rays from an object. If the distance between lens set 11 and optical sensor 12 (back focal length, BFL) is fixed, the lens can only show clearly objects at its hyperfocal distance (e.g. 2-3 meters away). For the camera to shoot objects clearly at varying distances (for example at a close distance), the distance between lens set and sensor must be adjusted usin...

AI Technical Summary

Benefits of technology

[0008] The primary object of the present invention is to provide an auto-focusing device with voice coil motor for position feedback, which uses a magnetic sensor to detect the lens position for position feedback during auto-focusing. The present invention features fewer components, simple configuration, small size, lower cost, positioning precision, and low noise.

[0009] Another object of the present invention is to provide an auto-focusing method using voice coil motor for position feedback, which achieves precision positioning by obtaining the functional expression between voltage detected by the magnetic sensor and lens position and using it to provide feedback of lens position during auto focusing.

[0010] Yet another object of the present invention is to provide an auto-focusing device with voice coil motor for position feedback, which uses an electromagnetic actuator formed by two coils and two stacked permanent magnets with opposing poles to drive the lens to engage auto-focusing. Such design increases the magnetic flux density, enables full utilization of the effective magnetic field of permanent magnet, increases drive efficiency, and saves power consumption.

Problems solved by technology

Such design increases the magnetic flux density, enables full utilization of the effective magnetic field of permanent magnet, increases drive efficiency, and saves power consumption.

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